作业帮0.5x+0.7y=35 x+0.4y=40
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0.5x+0.7y=35 x+0.4y=40
0.5x+0.7y=35 x+0.4y=40
0.5x+0.7y=35 x+0.4y=40
0.5x+0.7y=35 (1)
x+0.4y=40 (2)
(1)×2-(2)得
y=30
把y=30代入(2)得
x=22
∴x=22
y=30
如图，这类方程组都是这样解
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